1. Directly go to General--Restore--select Restore all settings. See if it works. 2. The problem with the headphone jack, plug the headphones in a few more times, unplug them and press the volume increase or decrease. It would be fine if the screen displays "Ring Tone". If it displays the headphone volume, continue plugging and unplugging. 3. The speaker is burned out. . . 4. The sound on the side of the phone is locked